The present invention is directed to an assembly including an axially elongated screw pin arranged to be screwed into a tooth. The screw pin has an axially extending threaded part followed by an axially extending engagement part. A driven member is engageable with the engagement part for driving the threaded part of the screw pin into a tooth. The driven member and the engagement part are arranged so that the driven member is disengaged from the screw pin when the pin is fixed in the tooth.
Known parapulpal or dentine screw pins are screwed into the dentine portion of the tooth, that is, the portion of the tooth completely outside the pulp. Such pins have a threaded part and an engagement part which can be temporarily held by a gripping member. The gripping member includes a rod-like part which at one end can be detachably connected with the angle piece of a dental drill and the other end contains a hole or slot in which the engagement part can be gripped. An annular notch or groove is provided between the threaded part and the engagement part which forms a predetermined breaking point.
When such a dentine screw pin is to be inserted, initially a borehole is drilled in the tooth. Next, a pin is removed from a screw pin supply container using forceps or the like and the pin is inserted into the gripping member positioned in the angle piece of a dental drill. Next, the screw pin is mechanically screwed into the borehole using the dental drill as the drilling or driving member. When the screw pin is fixed in the tooth it breaks off at the annular groove. The threaded part and a head part, possibly formed as a portion of the threaded part, remains in the tooth while the engagement part of the pin remains in the gripping member.
Accordingly, in such a screw pin the engagement part is separated from the threaded part which remains in the tooth so that there is a material loss which results in increased costs. Another disadvantage is that the engagement part must be removed from the gripping device in a separate operation and the insertion of the screw pin in the gripping member is a relatively time-consuming operation. These various operations are made more difficult because of the small dimensions of the screw pin where the threaded part has a maximum diameter of about 1 mm and is usually in the range of 0.35 to 0.8 mm.
Further, there are known screw pins each having two threaded parts and two annular grooves each forming a predetermined breaking point. One of the annular grooves is located between the engagement part and the threaded part and the other is arranged between the two threaded parts. With this construction, the front threaded part is screwed into the borehole in a tooth so that the threaded part fixed in the tooth breaks off from the screw pin at the location between the two threaded parts. Subsequently, the rear threaded part is fixed into another borehole and it breaks off from the engagement part at the annular groove between them. With this screw pin construction, the material loss is reduced relative to the screw pins described above which have only one threaded part. Screw pins with two threaded parts, however, have the disadvantage that they are more difficult to handle because of the original greater length. Moreover, it is possible in the screwing-in operation that the screw pin may break off between the rear threaded part and the engagement part instead of between the two threaded parts so that the rear threaded part must be separated from the front threaded part and it can no longer be used resulting in a loss of material.